In offshore production of hydrocarbons (oil and/or gas) it is known to supply natural gas from an underground source to a field installation for gas treatment, the gas after possible purification being transferred in compressed form from the field installed on to a LNG tanker, where at least a part of the gas is liquefied before being transferred to storage tanks on board the tanker. For a further description of this system reference may e.g. be made to U.S. Pat. No. 6,003,603
U.S. Pat. No. 6,434,948 describes a system for production, storage and export of liquid natural gas (LNG) from an Floating Production Storage and Offloading (FPSO) vessel with an LNG liquefaction plant to an LNG tank. The LNG tank is provided with a buffer storage capacity for temporary storage of the continuously produced LNG during the absence of an LNG tank vessel.
In these known systems, nothing is mentioned on how to deal with the remaining gas produced after oil processing.
The present solution permits to eliminate expensive and non environmentally friendly solutions such as gas re-injection or flaring to get rid of the associated gas produced on the field development. The present invention also proposes a solution which would enable an offshore hydrocarbon production unit and an offshore liquefaction unit to work in conjunction, with no interdependence between their activities which increases the system uptime and reliability.